A hydroxyl group containing new cardo diamine monomer was synthesized, namely 9,9-bis (hydroxy- (4'-amino(3-trifluoromethyl)biphenyl-4-oxy)-phenyl)-9H-fluorene (mixture of isomers, HAPHPF). HAPHPF, along with a sulfonated diamine monomer, 4,4'-diaminostilbene-2,2'-disulfonic acid (DSDSA), was used to prepare a series of new sulfonated copolyimides by polycondensation with 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). The degree of sulfonation (DS < 1) was adjusted by the feed ratio of DSDSA/HAPHPF and the copolymers were named as DHN-XX, where XX denotes the mole percentage of DSDSA (XX = 50, 60, and 70). The copolymers showed high molecular weights. The copolymer structure and composition were confirmed by FTIR and NMR techniques. Copolymer membranes were prepared through solution cast route by using dimethyl sulfoxide as a solvent. The membranes showed high thermal, mechanical, hydrolytic and peroxide radical stability, and low water uptake and low swelling ratios. Well-separated hydrophilic and hydrophobic phase morphology was observed in TEM and AFM images of the copolymer membranes and was further supported by the SAXS studies. The proton conductivity of the DHN-70 was as high as 97 mS cm at 80 °C and the value is significantly higher than that of the nonhydroxylated analogue. The membranes also showed superior microbial fuel cell (MFC) performance, similar like Nafion 117 under similar test conditions. The chemical oxygen demand removal values provide substantial evidence that the fabricated membranes can be utilized in bioelectrochemical systems.

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Significant Coulombic loss in microbial fuel cells (MFCs) is attributed to utilization of the substrate and electrode space by nonexoelectrogenic micro-organisms. Selective enrichment of electrogens by inoculum pretreatment could offer solution to this problem. This study evaluates the effect of inoculum pretreatments such as acid treatment (pH levels of 4.0 and 5.3, via the addition of 0.1N H2SO4), heat, aeration, and ultrasonication on the performance of MFCs. Heat, ultrasonication, and acid pretreatments at pH of 5.3 were found to have an incremental effect on the power generation. MFC inoculated with acid-pretreated sludge at pH 5.3 produced a power density of 2.186 W m–3, which was ∼7 times greater than that produced by a control MFC inoculated with untreated sludge. MFC inoculated with aeration-pretreated sludge produced a slightly lower power density than control MFC. Acid pretreatment at pH of 4.0 was found unfavorable. Acid pretreatment at pH 5.3 was observed to be the most effective inoculum pretreatment, followed by ultrasonication and heat, for improving the Coulombic efficiency of MFCs.

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